Increasingly stringent environmental regulations have been one driving force in the development of Solid Oxide Fuel Cell technology. Widespread attention has been received for various potential commercial applications, due in part to the ability to produce electrical power from relatively small reactors that can be supplied with a liquid hydrocarbon feed. The high fuel-to-electricity conversion efficiency of solid oxide fuel cells leads to lower carbon dioxide emissions per kWh output of useful energy, while the emissions of various harmful chemicals, such as NOx, SOx, and unreacted hydrocarbons, are virtually zero. Applications targeted for solid oxide fuel cells include distributed and centralized power generation, vehicle propulsion, remote area power generation, marine, military and aerospace applications.
One problem, however, that is experienced with solid oxide fuel cell technology comes from the various sulfur compounds that may be present in the hydrocarbon feed that is supplied to the cell. The anodes of the solid oxide fuel cell are typically nickel based and can be readily poisoned by sulfur compounds that are commonly found in hydrocarbon fuels. As a result, desulfurization of the hydrocarbon feed is a necessary step for all solid oxide fuel cell systems that utilize nickel pre-reforming, anodes and a hydrocarbon feed. Commercially available hydrocarbon desulfurization processes require hydrogen gas, either generated or stored on site, for use in a hydrodesulfurization unit, where a portion of high molecular weight sulfur compounds present in the liquid hydrocarbon can be converted to hydrogen sulfide. The hydrogen sulfide can subsequently be removed by a bed of zinc oxide adsorbents.
The hydrodesulfurization systems typically consume large quantities of hydrogen, depending on the quality and the sulphur content of the fuel supplied to the desulfurization unit. For potential on-board vehicle applications, hydrogen storage becomes a major technical and economic challenge due to the space limitations of the vehicle. Thus, the need exists for the development of means for localized on-demand hydrogen generation using the available fuel from within the vehicle architecture.